This invention relates generally to a device used in the treatment of neurological disorders, especially pain and motor dysfunction by electro-stimulation of nerve fibers of the spinal cord, and more particularly to a novel combined assembly of an electrode and telescoping lamina hook that is more accurate in establishing a clinically effective placement of the electrode terminals, and more reliable in maintaining the position of the electrode itself, relative to the target fibers of the spinal cord and.
The use of electrical stimulation for the purposes of alleviating pain and the treatment of other neurological afflictions has been utilized for a number of years, and in many instances has become the standard of care. In new applications, as well, electrical stimulation of components of the nervous system continues to show significant therapeutic promise.
More particularly, in the spine, the original approach to electrical stimulation was to place multiple electrical leads directly onto the dura around the spinal cord. In such a procedure, the laminae of a sequence of vertebrae were removed so that the leads could be placed in a spaced apart relation along the central posterior axis of the spinal cord. This approach required a substantially invasive procedure in which bones and tissue were displaced or removed. In addition, the high frequencies of electrode migration from the target site or sites rendered the entire procedure suspect.
Subsequent iterations of spinal cord stimulation devices were implanted much less invasively, generally by percutaneous positioning. The first generations of this approach were immediately advantageous over the prior methods, insofar as they were carried out using local anesthetic as the electrodes were guided into position with the use of a fluoroscope. These early non-invasive procedures continued to use single lead electrodes, thus requiring a plurality of separate implantations. In addition, the leads would still easily become dislodged and migrate from the desired treatment site, usually becoming ineffective, but sometimes having actively negative effects on other nerves. These limitations and failures associated with multiple implantations of single lead electrodes briefly caused a reversion to the older, more invasive approach.
In an attempt to unify the multiple leads necessary for spinal cord stimulation into a single electrode, thereby attempting to bring the state of the art back to non-invasive procedures, designs from the cardiovascular art, i.e., pacemakers, et al., were modified for use in the spine. Multiple lead electrodes had been used in the cardiovascular field for some time, and were generally designed to provide stimulation to a variety of points on the surface of the heart. The modifications of these leads included strengthening both the leads and the structure containing the leads for the stresses of the spine, reducing the diameter of the leads to a size more appropriate for use in the spine, and alternatively providing either a removable or permanent rigid wire within the electrode to enhance placement. Unfortunately, while eliminating some of the causes associated with electrode migration, and reducing the number of electrodes which could migrate, the advances did not address the fundamental inability to fix the electrode at the appropriate location. This problem has been, and continues to be a significant drawback to the use of spinal cord stimulation in the regular treatment of pain.
Accordingly, there is a need to provide a spinal cord stimulator assembly that increases the accuracy of the placement of the electrode terminals and reduces the incidence and complications associated with the migration of the electrode.
The invention provides electrode assemblies for use in spinal cord stimulation that may be used in conjunction with standard and/or advanced electrical signal sources. Each of the electrode assemblies has at least one telescoping electrode that increases the accuracy of the placement of electrode contacts along a spinal cord, and a hook structure that reduces the incidence of, and complications associated with, the migration of the electrode. A variety of different embodiments of the invention are contemplated, exemplary ones of which are disclosed herein.
In a first embodiment, the invention includes a spinal stimulation electrode assembly including at least one wire lead having a proximal end adapted to couple to an electrical signal generator; a lamina hook having a blade hooking in a hooking direction; an electrode adapted to telescope from the blade in the hooking direction and having at least one electrical contact formed thereon that is electrically coupled to the wire lead; such that when the hook is disposed on a lamina of a spine and the electrode is telescoped from the blade, the electrical contact is positioned adjacent the spinal cord and an application of an electrical signal to the proximal end of the wire lead causes an electric potential to be applied to the spinal cord.
In an aspect of the invention, the blade has a bore extending therethrough and the electrode is adapted to telescope from the bore.
In another aspect of the invention, the assembly further comprises an electrode lock that can be used to lock the electrode in a telescoped position. The electrode lock can comprise a rough surface on the electrode, a rough surface on the bore, and a cap having a rough surface that frictionally engages the electrode""s rough surface and causes the bore""s rough surface to frictionally engage the electrode""s rough surface when the cap is closed.
In yet another aspect of the invention, the hook further comprises a head that can be used to couple the hook to a bone of the spine when the hook is disposed on the lamina. The head can accordingly include a hole through which a wire may be passed and tied to the bone.
The wire lead can comprise a plurality of wire leads and can be encased in an insulating and flexible elastomeric sheath; the electrical contact can comprise a plurality of electrical contacts; and the hook can comprise an insulating and flexible elastomeric coating.
In a second embodiment, the invention includes first and second wire leads each having a proximal end adapted to couple to an electrical signal generator; a lamina hook having a blade hooking in a hooking direction; a first electrode adapted to telescope from the blade in the hooking direction and having at least one electrical contact formed thereon that is electrically coupled to the first wire lead; a second electrode adapted to telescope from the blade in an opposite direction from the hooking direction and having at least one electrical contact formed thereon that is electrically coupled to the second wire lead; such that when the hook is disposed on a lamina of the spine and the first and second electrodes are telescoped from the blade, the electrical contacts are positioned adjacent the spinal cord and an application of electrical signals to the proximal ends of the wire leads causes electric potentials to be applied to the spinal cord.
In an aspect of the invention, the blade has a forked bore extending therethrough and the first electrode is adapted to telescope from a first branch of the bore and the second electrode is adapted to telescope from a second branch of the bore.
In another aspect of the invention, the assembly further comprises an electrode lock that can be used to lock the electrodes in their respective telescoped positions. The electrode lock can comprise a rough surface on the first electrode, a rough surface on the second electrode, a rough surface on the bore, and a cap having a rough surface that frictionally engages one of the rough surfaces of the electrodes and causes the bore""s rough surface to frictionally engage the other of the rough surfaces of the electrodes, and the rough surfaces of the electrodes to frictionally engage one another when the cap is closed.
In yet another aspect of the invention, the hook further comprises a head that can be used to couple the hook to a bone of the spine when the hook is disposed on the lamina. The head can accordingly include a hole through which a wire may be passed and tied to the bone.
Each of the first wire lead and the second wire lead can comprise a plurality of wire leads and can be encased in an insulating and flexible elastomeric sheath; each of the electrical contact of the first electrode and the electrical contact of the second electrode can comprise a plurality of electrical contacts; and the hook can comprise an insulating and flexible elastomeric coating.
In a third embodiment, the invention includes first and second wire leads each having a proximal end adapted to couple to an electrical signal generator; a lamina hook having a blade hooking in a hooking direction, the blade having an undersurface that seats adjacent to a spinal cord when the hook is disposed on a lamina of a spine, the undersurface having at least one electrical contact formed thereon that is electrically coupled to the first wire lead; an electrode adapted to telescope from the blade in an opposite direction from the hooking direction and having at least one electrical contact formed thereon that is electrically coupled to the second wire lead; such that when the hook is disposed on a lamina of a spine and the electrode is telescoped from the blade, the electrical contacts are positioned adjacent the spinal cord and an application of electrical signals to the proximal ends of the wire leads causes electric potentials to be applied to the spinal cord.
In an aspect of the invention, the blade has a bore extending therethrough and the electrode is adapted to telescope from the bore.
In another aspect of the invention, the assembly further comprises an electrode lock that can be used to lock the electrode in a telescoped position. The electrode lock can comprise a rough surface on the electrode, a rough surface on the bore, and a cap having a rough surface that frictionally engages the electrode""s rough surface and causes the bore""s rough surface to frictionally engage the electrode""s rough surface when the cap is closed.
In yet another aspect of the invention, the hook further comprises a head that can be used to couple the hook to a bone of the spine when the hook is disposed on the lamina. The head can accordingly include a hole through which a wire may be passed and tied to the bone.
Each of the first wire lead and the second wire lead can comprise a plurality of wire leads and can be encased in an insulating and flexible elastomeric sheath; each of the electrical contact of the undersurface and the electrical contact of the electrode can comprise a plurality of electrical contacts; and the hook can comprise an insulating and flexible elastomeric coating.